Welcome to meteorological fall

A developing thunderstorm over the St. Lawrence River off Ile Perrot on Thursday, August 27. Summer 2026 will be remembered across Canada for wildfires, flash floods and tornadoes. In Montreal, our weather seemed constantly unsettled, as if Mother Nature was irritated. (Valley Weather Photo)

Back to school, sunsets before 7pm, my snow clearing contract arrives as well as my tire change reminder for October. It must be September in Montreal!

September 1st marks the start of meteorological fall, statistically summer is behind us. The nights grow longer quickly, we see more dew and fog, and already, there is a hint of colour in the trees that will only increase over the coming days. 

The summer months in Montreal flew by at lightning speed as they often do. It was an odd summer to say the least, warm and humid, but nothing earth shattering as far as extreme heat is concerned. Officially the airport managed only seven 30C days, and only one heatwave during the first week of July. It was a wet summer, with the rain falling in bunches, including the June 20 storm that dumped 50 to 200mm on the parts of the city, mainly the West Island and South Shore. 

The flash flooding from the July across parts of the West Island of Montreal will probably end up being the weather story of the year. 

In terms of temperatures, the summer will end warmer than normal, but not record shattering. The average temperature at Trudeau Airport was 20.5C for June (normal 19.0C), 22.9C for July (normal 21.7C), and 21.1C for August (normal 21.1C).

As mentioned it was a wet summer, with precipitation falling on 10 of the 13 summer weekends since June 1st.

What can expect in September and beyond? An El Nino (the warming of the equatorial Pacific Ocean) is well underway, and expected to become a super El Nino. We have already witnessed the results of this across North America, with an active fire season, along with surpassed heat here in the east. The Atlantic hurricane season has also much quiter than normal to date.

The fall is expected to be warmer-than-normal in Montreal, along with less precipitation. Winter will be challenging. Historically El Nino winters produce warmer temperatures along with less snow, but moisture latent southern systems tend to still produce heavy precipitation to the St. Lawrence Valley. This often results in freezing rain or mixed precipitation for Montreal. The great Ice Storm of 1998 occurred during an El Nino winter. Time will tell